Slurry classification



y 2, 1940- J. s. FASTING I SLURRY CLASSIFICATION Filed May '20, 1938 ATTORNEYS Patented July 2, 1940 PATENT OFFICE 2,206,721 sLumtY CLASSIFICATION Johan Sigismund Fasting, Copenhagen, Denmark, assignor to F. L. Smidth & Company, New York, N. Y a corporation of New Jersey Application May 20, 1938, Serial No. 209,010 In Great Britain May 20, 1937 3 Claims.

are especially useful for classifying slurry made of cement raw materials, an application of the invention for that purpose will be illustrated and described by way of example.

In the production of cement according to one method, a slurry of ground raw materials is pro duced, and separation of such slurry into fractions may be desired for various purposes, as for 20 ticles so that the former may be subjected toa further grindingaction. Also, it may be desirable, on occasion, to effect separation of particles which, although of approximately the same size, are of different materials.

In the practice of the invention, the desired classification is accomplished by applying the slurry in a thin layer to the circumferential surface of a rotatingbody of revolution, such as a cylinder, from which the individual particles are thrown off differentially, and intercepting and separately collecting the particles thrown from the surface of the body at different points in its rotation. The forces-to which the particles are subjected during their movement with the rotating body depend upon a number of factors, such as the size and weight of the particles, the na-, ture of the surface of the particles, their chemical composition, the nature of the slurry liquid, etc., and these factors are employed in the new classifying operation. Thus, since the centrifugal force acting on any particle is counteracted by the adhesion of the particle to the liquid present, and as the force is proportional to the weight of the particle, it is apparent that during the retation of the body, the larger, heavier particles will be thrown from the surface first, and the smallerparticles will be retained longer and, in some cases, may have to be removed mechanically. By intercepting and collecting the particles thrown. free at different points, a separation by particle size may easily be effected. If separation is desired of'particles of different kinds of material which have about the same example, to segregate the coarse and fine par-.

average size and nearly the same specific gravity,

one or more-substances, such as oil, may be added to the slurry or applied to the body to increase or decrease the'adhesion of some of the particles in comparison with the remainder. The particles thrown free in accordance with their varying degrees of adhesion may then be separately inter cepted and collected.

For a better understanding of the invention, reference may be had to the accompanying drawing in which thesingle figure is aview in vertical cross-section of one form of 'apparatusconstructed and operating in accordance with the principles of the invention.

In the apparatus illustrated in the drawing: a cylindrical drum l1 rotating on a horizontal y axis is mounted within a housing 18, the bottom IQ of whichserves as a container for a quantity of slurry into which the lower surface of the drum continuously dips to pick up a layer. Within the housing, a partition is mounted adjacent that side of the drum moving upward in normal operation, and the partition forms a trough from which leads a discharge chute 2!.

'At the other side of the housing is a partition 22 leading to a discharge chute'23, and having a horizontal edge lying close to the surface of the drum. The bottom of the housing is formed with a neck 24 in which is mounted a suitable agitator- 25 which may be driven at a low speed to maintain the slurry in uniform condition, and below the agitator is a valve chamber 26 containing a star valve 21 which controls flow through adischarge 2B, Slurry is supplied to the housing through an inlet pipe 29 through which the discharge chute 2| extends.

In the operation of the apparatus shown, particles in the thin layer of slurry picked up on the surface of the drum are thrown off during the rotation of the drum, the larger heavier particles passing upward along the paths indicated by the arrows C to strike the top of the housing and fall back into the trough at the side of the partition 20, from which the particles leave through the chute 2|. Lighter particles are thrown from the drum along the paths indicated by the arrows D, striking the top and side walls "of the housing and partition 22, so that these particles all pass out of the housing through the chute 23. Heavier, coarser particles, which strike the under side of the trough or fail to leave the drum and pass off through the discharge chutes 2i and 23, return to the body of slurry 4 in the bottom of the housing and settle to the bottom thereof whence they may be removed from time to time through the valve 21.

wiflitheapparatus described, it is possible to exclude from the mean-action obtained in the apparatm, all particles or a size or speciilc gravity a predetermined maximum, and by the material to successive treatmentaitistoreduoe to a minimum the amounto! liner or lighter particlesadhering to the coarser, heavier ones, so that an emcient into fine and coarse fractions is ch- 10 tained. Variation of the characteristicsoi the particlesintheiractionsobtained is secured by the relative pofltion oi the rotating body. or bodies and the partitions, or by changingthespeedotrotationoi'thebody. Intheuse 15 of the apparatus to obtain separation of particles which are of approximately the same \size, but of diiierent materials, a substance is either added totheslurryorappliedtothe drum,whichhas the characteristic oi? varying the adhesion to go the drum of the particles of the different materials. A sumcient quantity of such a substance is then used to insure that the particles'of one material will be retained longer or thrown 011 more rapidly than the particles of the other materials,asthecasemaybe,andinthis way, classification of the slurry particles may be made according to materials, rather than according to particle size or other physical characteristics.

I claim:

1. Apparatus for classifying slurry which comprises a housing containing a body of slurry at the hottom thereof, a drum mounted for rotaiionwithin the housing and dipping into the body of slurry, an inlet for introducing slurry 35 into the housing, a partition within the housing receiving particles thrown from the drum in the first part or the rotation of the latter and intercepted by the housing, an outlet for the particles receivedon said partition, a second partition ticles settling from the body of slurry in the I housing. h

2. Apparatus for classifying slurry which comprises a housing containingv a body of slurry at the bottom thereof, a drum mounted ior rotation within the housing and dipping into the body of slurry, an inlet for introducing slurry into the housing, a partition within the housing receiving particles thrown from the drum in the first part of the rotation of the latter and intercepted by the housing, an outlet for the particles received on said partition, a second partition within the housing receiving particles thrown from the drum in the later part of the rotation of the drum, an outlet for the particles received the particles leaving the body and separately collecting the particles thrown from parts of the surface in difierent angular positions.

JQHAN srarsmmp FASTING.

' ticlesto be thrown oflf differentially, intercepting 

